1. Field of the Invention
This invention relates generally to methods for scrambling and encrypting information embedded in a video program that is transmitted over the air, cable, satellite or telephone lines, or that is recorded on a video cassette tape.
2. Description of the Related Art
Television programs can include closed captioning and other information embedded in the program. This information can be embedded in the vertical blanking interval (VBI) lines (described below) of a television video signal. A VBI decoder in a VCR or a television is used to retrieve the closed captions, which are for the hearing impaired, and other information from the VBI lines. The closed captions are then displayed as text on the television monitor along with the video.
Other information can also be embedded in the VBI lines. For example, a directory to programs can be embedded in the VBI lines. The directory can either be transmitted in the VBI lines during a transmission over the air, cable, satellite or telephone lines or stored in the VBI lines of a video cassette tape along with the programs on the video cassette tape. The directory can then be used to control a video cassette recorder (VCR) to access programs on the video cassette tape. Such a system is described in the above mentioned application Ser. No. 08/066,666. Other information in the VBI lines can include channel specific program guide (CSPG), program related information (PRI), Instant Information (II), video magazine (V(M)) packet, and tape identification, program number and absolute address (TPA) packet, which are described below.
Since the information provides valuable services for users, it is necessary to control access to the information to only authorized users. Otherwise revenue for the services cannot be collected.
Accordingly, there is a need in the art for methods for scrambling and encrypting information embedded in a video program that is either transmitted or that is recorded on a video cassette tape. There is also a need in the art for methods for descrambling and decrypting information embedded in a video program.